Fig. 6

Fed-batch fermentation for GadB expression and GABA production of BL21(DE3)/pET20b-torA-gadB. GadB expression and GABA fermentation was performed in the same fermenter. The fermentation was done in two terms; (1) Culture for expression of GadB (without producing GABA). (2) Production of GABA with addition of MSG to the medium (with or without heat activation). Cells were grown at 37 °C for 28 h for expression and secretion of GadB. Then pH was adjusted to 4.6 and temperature was kept at 50 or 37 °C, and 650 g dry MSG was added in several batches in the same bioreactor. a Time profile of GadB expression at 37 °C and GABA production at 37 °C. b Time profile of GadB expression at 37 °C and GABA production at 50 °C. Curves of residual glycerol, cell density, intracellular and extracellular GadB activities, and GABA concentrations are shown